import java.util.Scanner;

public class Test1 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int n = in.nextInt();
            for (int i = 0; i < n; i++) {
                int len = in.nextInt();
                int k = in.nextInt();
                in.nextLine();
                String str = in.nextLine();
                int count = 0;
                int ret = 0;
                for (char c : str.toCharArray()) {
                    if (c == 'W') {
                        count++;
                        if (count >= 3) {
                            ret += k;
                        } else {
                            ret++;
                        }
                    } else {
                        ret--;
                        count = 0;
                    }
                }
                System.out.println(ret);
            }
        }
    }
}
